Variable coupling tuning coil



E M. MARKER, JR

VARIABLE COUPLING TUNING COIL Feb. 10, 1970 2 Sheets-Sheet 1 Filed Nov. 3. 1967 INVENTOR. 22x2 Mj%az:%z:e/2r M ATTORNEYS Feb. 10, 1970 E. M. MARKER, JR 3,495,201

VARIABLE COUPLING TUNING COIL Filed NOV. 3, 1967 2 Sheets-Sheet 2 IN VENTOR. Zdzgz zz M/farisz; 52

United States Patent. Oflice 3,495,201 Patented Feb. 10, 1970 US. Cl. 336-90 6 Claims ABSTRACT OF THE DISCLOSURE Adjustable coupling tuning coil assembly including a tube having one or more coils wound about a portion thereof, a coil form having a second coil or coils wound thereon and slidable along the tube, and a coupler in threaded engagement about the coil form, the coupler being rotatable from outside the container in which the assembly is located to thereby vary the axial spacing between the coils on the tube and those on the form and consequently vary the magnetic coupling between the coils.

BACKGROUND OF THE INVENTION This invention is in the field of tuning coils of the type used in radio and television equipment wherein it is desirable to provide a means for adjusting the coupling between the coils after the assembly has been placed in its metallic container. Heretofore, the critical adjustment of the coupling of the coils had to be made before the coil assembly was placed in its container so that final adjustment of the coupling between the coils after assembly was impossible.

SUMMARY OF THE INVENTION In the adjustable coupling tuning coil assembly of the present invention, there is provided a base which is snugly received within the container, and a tube is secured to or is integral with the base. One or more coils is wound around a portion of the tube and the coil leads are connected to lugs which extend through the base at the bottom of the container. A coil form is mounted for sliding movement along the tube but prevented from relative rotational movement with respect to the tube. A second coil or coils is wound about the coil form. The coil form carries a threaded flange which is in threaded engagement with a coupler mounted coaxially with the tube and the coil form. The coupler has resilient means on it which act against the container to take up any slack in the assembly. The coupler also has a tool engaging portion extending through the container and accessible at the top of the container, whereby rotation of the coupler can be effected by means of a suitable tool. Rotation of the coupler, by virtue of the threaded engagement between it and the coil form, causes the coil form to move axially along the tube and thereby change the coupling between the two coil circuits. In addition, each coil may be provided with its own ferromagnetic slug. The Slug for the bottom coil is located in the lower portion of the tube and is accessible for adjustment from the bottom of the container, and a second ferromagnetic slug is located in the upper portion of the tube where it is accessible through the tool receiving portion of the coupler for adjusting the axial position of the slug in the tube from the top of the container. Furthermore, both slugs can be adjusted from one or the other ends of the container if required.

pling tuning coilembodying the improvements of the present invention;

FIGURE 2 is an enlarged fragmentary view in elevatron, with portions thereof broken away, of the upper portion of the assembly as shown in FIGURE 1, with the container thereof being removed for purposes of clarity;

FIGURE 3 is a cross-sectional view taken substantially along the line IIIIII of FIGURE 1; and

FIGURE 4 is a cross-sectional view taken substantially along the line IV-IV of FIGURE 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIGURE 1, reference numeral 10 indicates generally a variable coupling tuning coil assembly of the type with which the present invention is concerned. The assembly 10 includes a base 11 composed of a nonmagnetic, non-conducting material such as a thermoplastic resin. A plurality of lugs 12 extend through the base for connecting the coils and any other electrical components contained in the assembly with external circuitry. The base 11 may also be provided with receptacles for positioning cylindrical or disk-type capacitors. If desired, the assembly may rest on standotfs 13 provided in the base by lengthening the tube 14 or shortening the container 28.

A tube 14 which is composed of a non-magnetic electrically non-conductive material is held firmly within the base 11 or can be integral with the base 11. A coil 16 is wound about the tubular core 14 and while a single coil 16 is shown, it should be evident that more than one coil can be wound about this portion, depending upon the particular circuit involved.

Centrally of the tube 14 are provided segmental flange portions 17 which can be used to provide a stop for the axial movement of the movable coil to be described, and further can be used to anchor the top convolutions of the coil 16 to the tube 14. Since the segmental flanges 17 are composed of a thermoplastic material, the application of a hot iron to those portions will cause the segments 17 to fuse and cool into deposits which firmly hold the upper convolutions of the coil 16 to the tube 14.

A cylindrical coil form 18 is mounted over the tube 14 in sliding relation, with a key 19 being provided in the tube 14 and received in a slot on the inner diameter of the coil form 18 to prevent relative rotational movement between the coil form 18 and the tube 14 while permitting relative axial movement between the two. One or more coils 21 are wound about the coil form 18. At its upper end, the coil form 18 is provided with a larger diameter flange portion 22 which has external threads 23 thereon. The threads 23 are arranged to engage internal threads 24 on a coupler generally identified at reference numeral 26. As best illustrated in FIGURE 2, the upper surface of the coupler 26 includes a plurality of integral fingers 27 which bear against the inner surface of the top wall of a metallic container 28. These resilient fingers serve to take up any slack between the coupler 26 and the container 28 to prevent axial movement between the two. The container 28 has one or more lugs 39 struck therefrom and engaging the base 11 in order to maintain the pressure of the fingers 27 against the container 28.

At its upper end, the coupler 26 is provided with a collar portion 29 which extends through a suitable aperture provided in the top of the container 28, as illustrated in FIGURE 1. The collar 29 has an external hexagonal periphery 31 for receiving a hexagonal wrench to therebv accommodate rotation of the coupler 26 from outside the container. If desired, the collar 29 may have an internal hexagonal socket, or any other means may be provided for rotating the coupler 26.

The threads 24 on the internal wall of the coupler 26 are discontinuous because of the provision of a pair of oppositely disposed windows 32 centrally of the coupler 26. The provision of these windows has no significant effect upon the electrical or mechanical characteristics of the unit, but makes it considerably easier to mold the coupler with plastic molding machinery. Continuous threads may, of course, be utilized if desired.

The tube 14 has a tuning slug disposed therein, the tuning slug for the coil form assembly being identified at reference numeral 34, and that for the tube assembly at reference numeral 36. As best illustrated in FIGURE 4, the internal wall of the tube 14 is provided with a plurality of thin ribs 37. These ribs are composed of the plastic material of the tube and are relatively deformable. The outer diameters of the threads on the slugs 34 and 36 are greater than the diameter of the cylinder defined by the inside edges of the ribs 37 but less than the internal diameter of the tube 14. The ribs 37 are deformed by rotation of the slugs so as to permit the slugs to be accurately located axially within the bore of the tube 14. The provision of these ribs is not a distinct part of the present invention, since this type of assembly is described and claimed in Antalek et al., US. Patent No. 2,838,738.

An aperture 38 is provided in the base 11 so that a hexagonal wrench can be inserted into the basev into the hollow slug 36 to adjust the axial position of the slug relative to the coil 16. Similarly, the same tool can be inserted through the tool-receiving portion of the coupler 26 to engage the hollow interior of the slug 34. The axial positioning of the slugs 34 and 36 thereby determines the inductance of the coil circuits in which they are located. Terminals 40 are provided on the container 28 for grounding purposes or for attaching the entire assembly to other circuit components.

The change in coupling between the coil assemblies is accomplished in the following way. Rotation of the coupler 26 serves to move the coil form 18 relative to the tube 14 by virtue of the threaded engagement between the threads 24 of the coupler 26 and the threads 23 on the coil form 18. This relative axial movement, of course, changes the coupling between the coils. The pitch of the threads on the coil form and the coupler can be made sufficiently small so that a very fine adjustment of the spacing between the coils can be achieved.

It should be evident that various modifications can be made to the described embodiments without departing from the scope of the present invention.

I claim as my invention:

1. An adjustable coupling tuning coil comprising a base, a tube extending from said base, a first coil disposed along a portion of said tube, a coil form mounted for sliding movement along the external periphery of said tube, a second coil disposed about a portion of said coil form, said coil form including an externally threaded flange portion, a hollow coupler having internal threads threadedly engaging the external threads on said flange portion, and means preventing relative rotative movement between said coil form and said tube, whereby rotation of said coupler serves to move said coil form axially along said tube.

2. The assembly of claim 1 in which said base is received within a container and said coupler has an end portion accessible for rotation from outside said container.

3. The assembly of claim 1 in which said coil form has an externally threaded flange which engages internal threads on said coupler.

4. An adjustable coupling tuning coil assembly comprising a base, a container receiving said base in snug fitting relation, a tube extending from said base, a first coil wound about a portion of said tube, a coil form mounted for sliding movement along said tube, means providing a key and slot connection between said coil form and said tube to prevent relative rotative movement therebetween, a second coil wound about said coil form, a coupler disposed about said coil form, resilient means associated with said coupler and acting against said container to take up slack therebetween, means providing a threaded connection between said coupler and said coil form, and means accessible from outside said container for rotating said coupler to thereby move said coil form axially along said tube.

5. The tuning coil assembly of claim 4 which includes at least one ferromagnetic slug positioned within said tube and accessible from outside said container for axial displacement within said tube.

6. The turning coil assembly of claim 4 which includes a pair of ferromagnetic slugs positioned within said tube, said slugsbeing accessible from both ends of said container for axial adjustment along their associated coils.

References Cited UNITED STATES PATENTS 2,136,731 11/1938 Benner 336-129 XR 2,383,475 8/1945 Dodington 336-129 XR 2,430,990 11/1947 Moore 336-118 XR 2,441,047 5/1948 Wall 336-129 XR THOMAS J. KOZMA, Primary Examiner U.S.Cl.X.R. 

